Drafting compass



Oct. 28, 1930.- v. l.. BELL DRAFTING coMPAss Filed May 9, 1928 ATTORNEY Patented Oct. 28, 1930v j l UNITED i STATES 1 PATENTOF'FICE y l l f `1,779,725 Y VICTOR L., Biani.,k orrnneiiwoon, PENNSYLVANIA y DRAFTING c'oiviianass'v 1 Application filed Mays, 192s. serial No. 276,245;

f may then be scribed on the surface of theV drawing paper with but slight penetration of the pivot point into the paper.

As the pencil or pen point wears, in order to bring the point into Contact with the paper While the handle ofthe instrument isperpendicular to the surface vof the paper, it is necessary to press the pivot point deeper into the v drawing paper each succeeding `operation with the result that the point makes per- 20 manent unsightly pin holes.

An object of my invention is to provide a drawing instrument or bow lpencil or pen wherein the pivot point is yieldingly mounted so that, as the point wears, it may be .25 brought into working contact'with the paper 1 or surface by slight pressure applied at the handle which compresses a spring supporting the pivot point and prevents undue penetratioii of the point. Tilting o-f the instrument face is rendered unnecessary and slipping of the point from its vsocket in the surface is eliminated. 'i

A further object of my invention is to provide a drawing instrument having the abovenoted characteristics wherein the pivo-tpoint is mounted-on one arm of the instrument for 7 Y longitudinal movement and wherein a spring to yieldingly bias the point to its outermost positie-n. n

A further object of my inventionis to provide a drawing instrument or bow pencil or pen wherein the tension of the movable pivot point may be adjusted to obtain the required tension on the pivot point to prevent undue `penetration of the point regardless of wear of the working stylus. f'

A further object of my invention is to provide a drawing instrument having the abovewithin a receptacle for the pivot point serves noted characteristics that is simple in construction and inexpensive to manufacture. i

i These and other objects that will be made Y apparent throughout the furtherde'scri'ption of my invention are attained in Vthe-instrumeiitto be hereinafterdescribed and illu'so trated in -the accompanying Y drawings, wherein:V

' VFigure lisa view: partially insidefelevation and partially in Section5-of a draw'ving V60 instrument embodying features of my'invention;

Fig. 2 is 'an elevational view ofthe device v shown in Fig. 1, turned'ninety degrees;V

Fig.. 3 is a longitudinal sectional view in 65 enlarged scale of a-fragment of the instrumentshowii in Fig-l; and

Fig. 14 isa longitudinal sectional view of a j fragment 'of a modified form of instrument. Referring to the drawings wherein a bow pencil is illustratedV forvthe purpose of eX- a'mple, the instrument comprises the'usual bow pencil v construction with the 'exception of the mounting for the pivotpoint and consistsof a pair of integral resilient arms 5 and 75 6 having flexible portions 7 and 8, respectivelly, jointed at9 and'provided with a knurled `handle 11 that is adapted tobe gripped between the thumb and :lingers of the operator. 30 to bring the stylusinto contact with the surrllie arms are normally biased by the flex- `80 l ible portions to eXtreme separated angular gpositions and are adjusted by means of a v screw 12 pivote'd to the farm 5 -and'extending through an opening 13 in the arm. vA

thumb screw le upon the screw 12 may be H35 Y `adjusted tobring the arm 13 intothe desired relation.` Y Y A v Y! The arm 6 is provided'atiits free end with a: split ysocketforfclamp",15' for receiving'z-a pointed pencil stylus-16, theclamp lbeing con- Y trolled by a thumbscrew 17'. .The arm 55 is provided witha detachable extension' 18 having a pin 19 which snuglyffits into arecess 21' inthe arm 6. The extension ,18 is also provided with a'recess'V 22 that is'closed '95 point toits'outermost position,v asshownA inlou of pivotally connected arms, a clampcn onel arm for retaining. a marking stylus, the free ,Y

Fig. 4. The point 24is provided with the usual paper penetration tip or point 2T andV the pencil point or stylus is usually so adjusted that the points are in a plane normal to that of the handle ll, as shown in Fig. l.

As the point of thestylus 16 wears away, slight pressure on the handle ll` compresses the spring unt-il the stylus again engages the surface being marked. Readjustment Vof the stylus at frequent intervals is not necessary, as is the caso ywith presentinstruments and, accordingly, considerable time is saved. `All circles can be uniformly made and1 the ab senceof unsightly pin-holes'reisults .in a drawn ing of neat appearance.k Tilting of the instrument to ybring the stylus intocontact with the surface being marked is unnecessary, and the danger` of causing the pivot pointto .slip from its socketis eliminated; l Y K f vIn F ig. 4 I have 'shown ainodiiied form tially perpendicular to and towai'd the surfacefor bringingV the stylus into contact with thel'surface while' the pivot arm is held sub-` stantially perpendicular to the' surface.'v l

In testimony whereof, I have hereunto subscribed my name thisth day of May, 1928. A. .VICTAOR L1BELL.

of p'ointvmounting wherein the tensionof the vSpring. 26 is renderedadjustable, the mounting being provided with a screw plug 23 .that

is provided with a slot 28 for' receiving Spanner wrench, by means ofwliich the plugA Vmay be removed. To increase the tension. of

the spring 26, discs 29V are added untilgthe desired tension is obtained. v It is obvious that other means may spring adjustment.

While I have shown, for the. purpose of illustration, a bow penci-l it` will be understood that theinvention-is-equally applicable to;y bow-pens, since thepivot point may be depressed suiiiciently to bring both nibs of the bow pen in contactwith the surface being marked and since wearing of the nibs be 'employed to obtain makes longitudinal adjustment ofthe pivot point necessary.- It will be understood that the term stylus appearing in the claims applies to pencil and pen points.

- 7hile Iliave illustrated and described but 1 two embodiments of my invention, it will be apparent to those skilled in the art that varir ous changes, modifications, substitutions, ad-

ditions and omissions may be made therein claims. l

I claim as my invention: l. A drawing instrument comprising a pair end of the other arm having a receptacle for a pivot point, .a perforate plug for the receptacle, a pivot point slidably mounted in the plug,y and a spring' within-fthereceptacle engaging the inner end of the point for yieldingly urgingit to its outermost position.

2. A drawing instrument comprising a pair of pivotallyconnect-ed arms, one of which isrprovided with a non-yielding` stylus which becomes; shortened with use and the other 'with a longitudinally movable centering point about which the s'tylusis: rotated 

